[PATCH 3.19.y-ckt 092/102] iser-target: Fix possible use-after-free

[Kamal Mostafa]

3.19.8-ckt3 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Sagi Grimberg <sagig at mellanox.com>

commit 524630d5824c7a75aab568c6bd1423fd748cd3bb upstream.

iser connection termination process happens in 2 stages:
- isert_wait_conn:
  - resumes rdma disconnect
  - wait for session commands
  - wait for flush completions (post a marked wr to signal we are done)
  - wait for logout completion
  - queue work for connection cleanup (depends on disconnected/timewait
    events)
- isert_free_conn
  - last reference put on the connection

In case we are terminating during IOs, we might be posting send/recv
requests after we posted the last work request which might lead
to a use-after-free condition in isert_handle_wc.
After we posted the last wr in isert_wait_conn we are guaranteed that
no successful completions will follow (meaning no new work request posts
may happen) but other flush errors might still come. So before we
put the last reference on the connection, we repeat the process of
posting a marked work request (isert_wait4flush) in order to make sure all
pending completions were flushed.

Signed-off-by: Sagi Grimberg <sagig at mellanox.com>
Signed-off-by: Jenny Falkovich <jennyf at mellanox.com>
Signed-off-by: Nicholas Bellinger <nab at linux-iscsi.org>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 drivers/infiniband/ulp/isert/ib_isert.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/infiniband/ulp/isert/ib_isert.c b/drivers/infiniband/ulp/isert/ib_isert.c
index 960a36c..b7350d5 100644
--- a/drivers/infiniband/ulp/isert/ib_isert.c
+++ b/drivers/infiniband/ulp/isert/ib_isert.c
@@ -3316,6 +3316,7 @@ static void isert_free_conn(struct iscsi_conn *conn)
 {
 	struct isert_conn *isert_conn = conn->context;
 
+	isert_wait4flush(isert_conn);
 	isert_put_conn(isert_conn);
 }
 
-- 
1.9.1